Which Intellivision games are "winnable"?

[intvnut]

Funny!

 

By the way, Utopia uses the EXEC model, right? Do you happen to have the EXEC API mapped out, or are you just discerning the PRNG function from the disassembly?

 

Various bits have been worked out over the years. Now here's one loop that boggles my mind:

$5452:    0001                   SDBD
$5453:    02BC 00D4 0030         MVII #$30D4,R4
$5456:    0001                   SDBD
$5457:    02B9 0072 0045         MVII #$4572,R1
$545A:    0004 0114 029E         JSR  R5,$169E
$545D:    0014                   DECR R4
$545E:    00A4                   TSTR R4
$545F:    0223 000A              BPL  $5456
$5461:    0281 0192              MVI  $0192,R1
$5463:    0089                   TSTR R1

It's calling the bounded-rand function $30D4 times. That's right, 12500 times. Why? WHY? And the value in R1 isn't even used for anything--the random number bound is in R0. And R0 seems to always be 0 when reaching this code, because it happens right after printing various strings:

       JSR     R5,     X_PRINT_R5              ; 543C   0004 0118 007B
       STRING  "SCORES"                        ; 543F  
       DECLE   $0000                           ; 5445   0000
       B       L_5452                          ; 5446   0200 000A
L_5448:
       JSR     R5,     X_PRINT_R5              ; 5448   0004 0118 007B
       STRING  "TOTALS"                        ; 544B  
       DECLE   $0000                           ; 5451   0000

It's calling the bounded RAND, but it never actually advances the random number generator, because the bounded-rand routine tests for 0 and short circuits. You can see it in the execution trace:

0000 0001 0162 0007 02E9 5452 02F5 5452 ----I-i-  SDBD               131093862
0000 0001 0162 0007 02E9 5452 02F5 5453 ----ID--  MVII #$30D4,R4     131093866
0000 0001 0162 0007 30D4 5452 02F5 5456 ----I-i-  SDBD               131093876
0000 0001 0162 0007 30D4 5452 02F5 5457 ----ID--  MVII #$4572,R1     131093880
0000 4572 0162 0007 30D4 5452 02F5 545A ----I-i-  JSR  R5,$169E      131093890
0000 4572 0162 0007 30D4 545D 02F5 169E ----I-i-  PSHR R5            131093903
0000 4572 0162 0007 30D4 545D 02F6 169F ----I---  PSHR R1            131093912
0000 4572 0162 0007 30D4 545D 02F7 16A0 ----I---  PSHR R2            131093921
0000 4572 0162 0007 30D4 545D 02F8 16A1 ----I---  MOVR R0,R1         131093930
0000 0000 0162 0007 30D4 545D 02F8 16A2 ---ZI-i-  BEQ  $17D2         131093936
0000 0000 0162 0007 30D4 545D 02F8 17D2 ---ZI-i-  PULR R2            131093945
0000 0000 0162 0007 30D4 545D 02F7 17D3 ---ZI-i-  PULR R1            131093957
0000 4572 0162 0007 30D4 545D 02F6 17D4 ---ZI-i-  PULR R7            131093969
0000 4572 0162 0007 30D4 545D 02F5 545D ---ZI-i-  DECR R4            131093981
0000 4572 0162 0007 30D3 545D 02F5 545E ----I-i-  TSTR R4            131093987
0000 4572 0162 0007 30D3 545D 02F5 545F ----I-i-  BPL  $5456         131093993

Crazy. I guess it's a delay loop that intends to cycle the random number generator, but fails to.

[cparsley]

Remember it's not a bug, it's a feature!